If that were the case then we'd expect a similar level of wonderful lines in the works of his contemporaries, but he was very clearly a standout wordsmith even

If that were the case then we'd expect a similar level of wonderful lines in the works of his contemporaries, but he was very clearly a standout wordsmith even compared with other fine writers such as Marlowe, Middleton, Webster and Jonson etc. It's not that his are the only works to have survived, they're simply the only ones we still speak of in regular conversation.